Lucario vs Aizen
by Jurassic Lion
Summary: In the hour of crisis on Sogyoku Hill, an unforeseen warrior arrives. With the Aura Lucario challenges the power of the most disgraceful Shinigami. *Action, crossover fight*


**Flying Lion: This was written for pure indulgence and not meant to be taken too seriously. Though it's different territory for me even though fanfiction is usually written purely for fun. This was even more so given the ridiculousness of this crossover. Enjoy.**

* * *

Saijin Komamura fell to the might of Sosuke Aizen. Ichigo could not believe the sight he bore witness to. How could both of them be Captains of the Gotei 13 yet have such a vast difference of strength? It plexed Ichigo as he had just fought Byakuya, also a captain, yet was easily taken down by Aizen with just one finger.

He could do nothing. He could barely crawl, let alone attempt to stand. Ichigo would do his damndest to try and stop Aizen yet all hope seemed lost. Aizen slowly approached Rukia Kuchiki. His zanpakuto was drawn out ready to go for the kill.

"Everything has gone according to my plan. Not Urahara, not even the entire Gotei 13 could have stopped me even if they tried. My goal is to break the barrier between hollows and Shinigami - you are no longer needed."

Rukia couldn't move. She could barely manage to stand the weight of Aizen's tremendous spiritual pressure. It was like a thunderous flood of rain seeping down from the heavens crushing her body. She trembled, knowing she couldn't run if she wanted, all the while Aizen's sword slowly swung down towards her.

Ichigo screamed a desperate cry. For someone. Anyone.

No one had seemed to notice the blur speeding across the hill in that instant. Aizen too absorbed in his momentary task and gloating didn't see the approaching figure making their way. Had he, he would have watched as Tousen and Gin were both disarmed and knocked back by a powerful force. The two Shinigami captains were struck so quickly that the blur had made it to their goal before they fell to the ground unconscious.

The blade never struck Rukia. The pang of metal clashing with metal rang out like lightning on the hill snapping Rukia and Ichigo out of their terror. Suddenly Rukia found herself not in the shadow of the villain who'd manipulated everyone, but at the side of Ichigo and Renji. She was seated down by someone who stood with their back towards Aizen.

The Fifth captain gasped. Rukia was gone from his sight. He looked around sensing her nearby the fallen and wondered just how she had managed to evade him. But the answer struck at the sight of the blue furred figure.

"There was no way Rukia could avoid my blade. But it makes sense if you're here, Lucario."

Ichigo had no idea what had happened. But Rukia was sitting next to him now. He barely registered anything when he spotted Lucario standing right in front of him. He did not know him at all. Nor did it seem Rukia knew as she was just as confused as Ichigo. Lucario turned away from the two facing Aizen straight down.

"You must forgive me for being late Aizen. I was busy dealing with your henchmen in Hueco Mundo. But now that it's done, all that's left is you."

"You must be mistaken. Gin - " Aizen stopped realizing the state of his lackeys. Lucario chuckled still walking forward towards the Captain.

"Your Arrancar army is no more. My allies and I saw to its decimation. Now all I have to do is kill you."

Aizen glared him down. Without another word he sheathed his zanpakuto. Holding out his fingers he began to summon the incantation of a kido spell to thwart Lucario's advance.

Ichigo recognized the gigantic black walls forming around the hill as the earlier technique - Bakudo 90 - which took out Captain Komamura. They surrounded Lucario fully and looked to take him down the same way as the fellow wolf. But Lucario's body glowed a bright, ocean blue, and the spell crumbled apart as Lucario unleashed his power. The force of it emitted much like Aizen's spiritual pressure, knocking Rukia off of her feet and even causing Aizen to stumble.

Lucario's body returned to normal. He merely watched Aizen before summoning a bluish orb to hand. Aizen didn't respond but ran forward drawing his zanpakuto. He was fast and would have cut down Lucario had not the canine been faster. Aizen stopped in his tracks as Lucario appeared in a flash behind him. The Shinigami was too slow and struck in the back.

"Watch the Power of Aura!"

Aizen was flung forward and flew across the hill. His body fell towards the edge into a great explosion of blue energy. Lucario stood straight, his paw smoking from the sheer heat of the energy emitted from it. All the while smoke rose from the site of the explosion and the earth at the side of the hill crumbling away.

"Rukia, who is that? Who is he?" Ichigo managed to ask. He looked to his friend who merely watched stunned.

"Lucario... I heard rumors, word of a wolfman, a member of the Gotei 13 that disappeared two hundred years ago. But I didn't think... it was true."

A yell echoed on the hill then. Rukia and ichigo looked towards the smoke as it dissipated. Then Aizen leaped out of it falling onto the ground. His clothes burnt and ruined, he tore off his captain's uniform leaving only his tattered shihakusho. The glasses on his face fell broken onto the ground as well.

Lucario began to laugh. Aizen looked up at the warrior as he stood in front of him. "Without those glasses you look exactly as you are. A pretentious little snot."

Aizen clenched the dirt of the hill with his fist. Blood dripped into the soil then. His glare seethed at Lucario with full rage and fury.

"Why... why did my shikai not have effect? I put you under my hypnosis in that moment-"

"Do you really not know? I thought you went to careful lengths to study any and all potential enemies, Aizen."

In truth Aizen wasn't sure what Lucario was getting at. He ran through his head all the data and information he knew of him. A member of the wolfman clan just like Sajin Komamura, an ally of the Gotei 13 who was not a Shinigami. There was the matter of his disappearance years ago as well. Yet nothing stood out as that potentially threatening.

He remembered studying Lucario years ago. As a student of the Shinigami Academy he had read the reports, heard the rumors, of the fighter who killed hollows without a zanpakuto. Rumored to be as strong as, if not stronger than, a captain class Shinigami. But Aizen was stronger than that. He had always been extraordinary. What could this missing fighter have to challenge him with?

Lucario shook his head then. Aizen looked at him before suddenly feeling the full force of Lucario's powerful punch into his stomach. The Shinigami fell backwards rather undignified like. His zanpakuto flew out of his hands to be caught by Lucario. The warrior held it above his head.

"This Zanpakuto - Kyoka suigetsu - it is a terrible, _fearsome_ weapon. To craft illusions and put anyone you so choose under your _spell_. To _trick_ the mind like that is indeed hard to stop. But you had the misfortune of _crossing_ my path."

The sword was then shattered. Aizen sat up watching the blade's pieces fall onto the ground. Lucario stretched, yawning lazily as he did so. The Shinigami seethed.

"So how - how are you able to!?"

Lucario sighed. Shaking his head he then summoned again, the powerful Aura sphere to his palm.

"I am not a Shinigami. Nor am I a hollow. Nor am I a human with spiritual power. But my power is far more ancient. I have the Aura."

Aizen could not believe his ears. But no doubt what Lucario said was exactly what he had heard. It was a form of fighting believed to have been mystical. But at best it was the power of an old died off religion.

"I remember. that silly, old, power couldn't be enough to stop - " Aizen was then silenced as the sphere was struck at him again. Though it was smaller it still was strong enough to injure him further. Lucario continued.

"The Aura _surrounds_ us. It _binds_ us, is in every living thing, and _all_ is bound to it's will. I was strong enough to challenge the strength of Shinigami, Aizen, because I trained my body to it's fullest height with the Aura. And the Aura is a powerful ally."

Aizen clenched his teeth. He would have stood had not the pain in his stomach ached so much. Lucario stood over the Shinigami now.

In all of that commotion Aizen hadn't realized the reaction of the Hogyoku. The sacred orb came back to his mind as he sensed it reacting in that instant. Lucario blinked all the while the artifact glowed brightly from Aizen's person. The Shinigami's gaze widened realizing his chance then and there.

Mustering his will, Aizen made way to stand. He held the Hogyoku in the palm of his hand directing it towards Lucario. The Aura warrior stood by watching the Shinigami as a mad look graced his features.

"You forget you uncivilized beast! I have the Hogyoku in my possession. I can still use it to become a higher being - I will destroy you as a god!" Aizen began to laugh hysterically. The man was a stark contrast to the cool collected strategist who quelled Ichigo and Renji so easily. Lucario's gaze narrowed.

"You've lost your mind."

The Hogyoku continued to glow. The energy emitted was just what Aizen had hoped for. His plans had changed and accelerated now. Without another word he began to summon his own spiritual pressure to enhance the orb. Then he would do as he initially sought - to become one with the Hogyoku.

Aizen however had been so caught up in focus of the relic that he missed the blur speeding towards him. He didn't even feel the tear of his flesh as his arm was torn apart in a millisecond. The Shinigami only knew that he was sent back again by a powerful punch and collided into the earth of the hill.

Lucario stood with the Hogyoku in hand. On the ground Aizen's entire left arm lay in a bloodied mess. He could sense what Aizen had intended and moved quickly to stop him. Ichigo and Rukia watched still, barely registering what had happened. They had one moment saw Aizen going mad and the next Lucario stood alone and Aizen was across the hill in a crater.

But it was not enough. Lucario turned around sensing the rise of spiritual pressure. Aizen stood one more, blood gushing from the hole where his arm once was. The man looked even more deranged than before.

"I just disarmed you Aizen. You'd be foolish to try and fight me."

Rukia could not suppress a chuckle. Ichigo rolled his eyes.

"You really believe

will stop me. You are a fool!" Aizen made a mad dash towards Lucario. The Aura guardian braced himself making a stance in defense.

The Hogyoku however zoomed from Lucario's grasp. This caught him off guard as the relic went back to Aizen. The Shinigami cackled then holding the item in his remaining hand. Suddenly it glowed even brighter and it's energy growing all the more wild in that instant.

Lucario could feel what was happening then. The orb cracked and began to ooze a purplish substance which swarmed all around Aizen's body. His spiritual pressure began to grow haywire to the point of affecting the very air itself. All the while Aizen laughed in pleasure as he was transformed in that moment.

At first the only visible change was the growth of his hair length. But the ooze forming about him suddenly fuzed turning Aizen into a white humanoid form. Giant large wings sprouted unnaturally from his back as did snake light appendages. His missing arm was replaced by a regenerated white limb with it's end resembling a sword. Finally his eyes changed into black orbs in addition to a third, grotesque purple eye from his forehead. His mouth grew unnaturally wide barring monstrous fangs.

"I see. So this is the form the Hogyoku wishes for me to take? Fine. I shall do as it pleases and kill Lucario!"

Aizen flew incredibly fast. But Lucario could still see him and braced himself as he swung his sword like arm. Lucario blocked the strike though felt the earth break beneath his feet. The monster did not hesitate further as one of his appendages began to emit a powerful cero blast. The beam firing quickly to hit Lucario.

The earth then exploded. Lucario however zoomed out of the smoke running at an extreme speed. He was so fast that he dodged Aizen's successive ceros which destroyed the earth. Ichigo and Rukia could merely watch in awe at the massive destruction occurring on the battlefield now. Neither was sure if it would even be standing at it's conclusion.

Lucario then neared Aizen. Aizen defended with his sword arm to parry Lucario's paw spikes. The two parried each other's blows each unable to make a direct hit. The blows rang sharply with cracks into the barrier of sound. Lucario used both arms to block Aizen's swing once more feeling the wind break from the sheer force of it.

The smirk on Aizen's face was not a good sign in that instant. It was then that one of Aizen's hollow like appendages pulled Lucario from behind. He was thrown about and flew across the ground of Sogyoku hill before crashing into a crater. Not hesitating any further Aizen fired several ceros precisely at Lucario. The explosion bursted then into a gigantic fireball large and powerful.

Many across the Soul Society could sense the enormous spiritual pressures emanating from the Hil. But even those who could not sense it knew now just what was happening at the sight of the massive explosion. Fighters all around in separate battles turned their attentions to the Hill wondering just what was happening.

Aizen growled like a beast then amused at his accomplishment. Fire spread from the explosion now basking Sogyoku Hill in a bright orange and smoke rose from it darkening the sky now. He was certain that his foe was now destroyed and rid of for good.

"Serves him. A creature like that has no place challenging a god beyond Shinigami and Hollows." Aizen cackled then. He turned away to finish his business with Ichigo and Rukia now.

But then the smoke suddenly blew away. Aizen turned back around at the sound of it before stopping in his tracks. Out of the smoke Lucario walked out, darkened by shadow, but clearly still in tact after Aizen's attack. Though as he came into more visible view it was clear that Lucario was injured, with bruises and scars all about his form.

"You just can't stay dead." Aizen seethed. Lucario growled as he pulled his twisted arm back in place.

"It seems I can't keep playing around. It's time to unleashed my ultimate evolution."

What this meant Aizen had no true idea. But he watched in anticipation as Lucario approached further. He stopped then and suddenly his entire body began to glow. The very wind itself blew back and the air sparked with electricity. Aizen closed his eyes then with dust and smoke swirling about as Lucario then transformed.

When he'd opened them Aizen was met with a new sight. Lucario's form had changed. He was taller, spikes shartper, covered in more yellow fur including his tail, and his limbs were red. To Aizen it seemed to have been a transformation for power.

"I see. You have a form similar to an Arrancar's own Ressureccion or a Shinigami's Shikai and Bankai. You're stronger than before. But it is futile, Lucario! You shall not - "

Lucario now stood in front of Aizen. He didn't notice him move. He didn't see it. He didn't even sense it!

When he did move Aizen didn't know. But it was impossible. Aizen's mind barelly had a chance to race when suddenly Lucario's fist flew through his chest.

Aizen fell back then and coughed up blood. Immediately his body began to regenerate with the white hollow substance oozing from the Hogyoku. Lucario moved quickly again throwing several punches battering Aizen around. Each blow was the strongest physical attacks the Shinigami had ever felt in his life. The pain was like that of the strongest steels.

In one moment Aizen attempted to fire back a cero in hopes of knocking Lucario back. But Lucario was quicker and sliced off the hollow like appendage. It bled and Aizen howled in agony from it. It was then Lucario wasted no time charging up a powerful Aura Sphere within his right palm and fired it.

The blast pierced Aizen's right side and shot out greatly into the distance. Lucario then stood back as it dispersed leaving Aizen standing as he was. The Shinigami then noticed his right arm was completely gone and part of his torso obliterated. His eyes panicked now watching Lucario who merely stood his ground.

In a desperate attempt Aizen shunpoed away. He hadn't gotten far only making it to the edge of the hill. Lucario grabbed the man by his shoulder holding him in place. Aizen looked back in fear as he for the first time felt utterly powerless.

He had then been thrown back and flew across Sogyoku hill. Aizen felt a tremendous amount of pain all over his entire body. The Hogyoku's power was slow now to heal him as the white ooze attempted to repair him. Lucario was quick and stood near the fallen enemy. Aizen looked back to him noting his gaze now. Confident, cool, unamused at having the advantage.

"You could argue me. But all of it, talks of being all knowing, all powerful, are futile. This is the end."

Lucario began to summon another powerful aura sphere in his palms. This was much larger than before and would certainly finish what Lucario had started. Aizen couldn't balk in defiance then. All that came to him in response was to cower.

Even if he'd screamed Aizen would not have been heard as the sound of the powerful blast of the Aura Sphere echoed from Sogyoku Hill. It rose up in a blue energy wave piercing even the sky above the Soul Society. Now the many who were making their way to the Hill could see even this and could not believe what was happening.

The dust began to settle then but Lucario needn't it to know what became of his foe. He could sense the life force fading now. The hogyoku he sensed breaking then and crumbling to dirt blowing away into the wind. Aizen let out a low raspy gasp until finally he could not make another sound.

Further back Ichigo and Rukia still sat as they were. They struggled to see what had happened until Lucario once again came into view. His body reformed back to his normal form. Though he was not their friend by any stretch the fact that he smiled assured them of their safety. And it was that which let them know that the hellish nightmare was over.

* * *

As Lucario had assumed, nearly all of the Gotei 13 had arrived soon after Aizen was killed. His mangled pathetic corpse was disposed of by the Kido Corps and all of the injured recovered by their loved ones. The Ryoka were taken care of as well now no longer considered criminals. Rukia too was cleared of her charges.

Lucario explained his situation to the Shinigami. Bringing to light his investigation all of Aizen's crimes were exposed now. Corroborated by Toshiro Hitsugaya and Rangiku Matsumoto, it was then that all of Aizen's accomplishments expulged. What caught the Shinigami's attention more was Lucario's secret work in Hueco Mundo in dispensing of the massive Arrancar army.

"You mean to say that Aizen had formed an alliance with the Hollow? Truly he was a despicable man."

"With no doubt Commander Yamamoto. But it was with the help of the Vizards and several spiritually powerful humans called Fullbringers that their destruction was assured."

Standing before the 13 in person Lucario was glad to get everything all off the table. Though he did not mention to Yamamoto that it was with the additional help of several female Arrancar that aided in defeating Aizen's arrancar for good.

The Captain Commander gave Lucario his leave then. With that and the assurance of repairing all the damage inflicted by Aizen, Lucario left for a moment of peace.

Retsu Unohana trudged up the lonely green hill in the Rukon District following the familiar spiritual signature she sensed. Standing alone was whom she expected, back facing her yet most likely already knew she was arriving.

"Two hundred years away from Soul Society. You stick around yet you don't drop by to say hi to me?" The fourth captain giggled as she stood by his side. Lucario looked to her before smiling back.

"Truthfully, it's been so long. Standing here puts me at ease."

"Well, you did slaughter an army of Arrancar and the biggest criminal Soul Society has had for centuries. You must be pretty tired."

"You make me sound like a serial killer Retsu."

The two shared a laugh then. Unohana kneeled down onto the grass then. Dropping formality Lucario sat down as well. He let out a long breath as he gazed out into the horizon beyond.

"Soul Society will need to be rebuilt. Plenty of work has to be done to repair Aizen's damage." Lucario noted solemnly. He yawned then still staring out into the horizon.

"Yes. But I am glad that you are here. You've truly saved us all." Retsu spoke softly. She blinked feeling Lucario then fall onto her lap. Lucario was now shamelessly fast asleep.

Smiling Retsu stayed as she was enjoying the peace and quiet of the moment.

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 **Flying Lion: This came about because, well, even though Bleach is one of my favorite series, Aizen is one of my least favorite villains and a prime example of how not to write them. There's just been better foes in media and he has just been a hax. So I wrote this fic which is a pure indulgence with one of my favorite characters, Lucario, beating the shit out of him. Hopefully even for a fic that was written just for fun it was at least an entertaining read. Plus I've wanted to write something with Lucario in the Bleach universe and a big, massive Shonen fight made sense.**

 **Read and Review ;)**


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